input: don't drop the first byte when user starts typing during loading

Precalculation of the multiline color data can be cut short when the
user is impatient and starts typing.  But this would drop the first
byte of whatever was typed -- not nice when it was just plain text,
but surprising and worse when the first keystroke was a command.

This fixes https://savannah.gnu.org/bugs/?48388.

src/color.c

@@ -401,10 +401,15 @@ void alloc_multidata_if_needed(filestruct *fileptr)
 bool key_was_pressed(void)
 {
     static time_t last_time = 0;
+    int onebyte;
 
     if (time(NULL) != last_time) {
 	last_time = time(NULL);
-	return (wgetch(edit) != ERR);
+	onebyte = wgetch(edit);
+	if (onebyte == ERR)
+	    return FALSE;
+	ungetch(onebyte);
+	return TRUE;
     } else
 	return FALSE;
 }